<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子模型</title>
    <style>
        #app{
            /* 内容盒子 */
            box-sizing:content-box;
            /* 修改为边框盒子 */
            box-sizing:border-box;
            width: 100px;
            border: 1px solid plum;
            padding: 10px;
            padding-top: 20px;
            padding-left: 30px;
            margin: 10px;
            margin-bottom: 40px;
            margin-right :80px; ;
            margin: 10px,20px,30px,40px;
        }
    </style>
</head>
<body>
    <div style="width: 100px;height: 100px;border: 5px solid palevioletred;">
        盒子模型
    </div>
</body>
</html>